Packet-protocol standards evolved to solve the present day problems associated with transferring voice, data, and video over telecom switches. For example, one present day IT protocols work at Layer 2 of the Open System Interconnection reference model (“OSI”). Data link layer devices, such as bridges and switches, operate in Layer 2 of the OSI to analyze incoming frames containing encapsulated packets, make forwarding decisions based on information contained in the frames, forward the frames toward the destination, control data flow, handle transmission errors, provide physical (as opposed to logical addressing, and manage access to the physical medium. In some cases the entire path to the destination is contained in each frame. In other cases, such as transparent bridging, frames are forwarded one hop at a time toward the destination.
Switches are used to segment a large LAN into several smaller LAN domains. Also, they can be used to connect LANs of different media, such as 10-Mbps Ethernet LAN with a 100-Mbps Ethernet LAN. Switches are also used to reduce collisions on network segments, because they provide dedicated bandwidth to each network segment. Switches forward and flood traffic based on Media Access Control (“MAC”) addresses, which are unique identifiers attached to most network adaptors (NICs).
One current bridging protocol, IEEE 801.1AH, also known as “Provider Backbone Bridging” (“PBB”) provides for a packet based infrastructure that allows for the efficient support of packet data, voice, and video applications. PBT is a variation of Provider Backbone Bridging (“PBB”), which allows carriers to provision engineer and protect point-to-point service. This technology is being deployed to help fill in the gaps in a typical Ethernet network by routing traffic and performing constraint based route management while protecting full QoS guarantees and providing extremely fast recovery rates after failures. PBT operates by adding statically configured routes to a nearly standard PBB network and its provisioning and management system allows a carrier to provision point-to-point trunks and services within an Ethernet network Each trunk is identified by a 16 bit VLAN ID and a 96 bit source/destination address pair.
PBT is now being updated to support carrier grade Ethernet by the addition of a path protection schema. PBT uses a provision/management system to configure the Bridge forwarding tables for the frames addresses. PBT itself is the modification of a switched network to shut off MAC learning in the core and the addition of a new Header for the traffic routing that consists of a MAC address, Working VLAN and Protection VLAN, and a service ID. Each PBT circuit is composed of a working path and a protection path that use different B-VIDs to access the same MAC address. The management must operate on both the working path and the protection path.
Essentially, all the tables that contain the MAC addresses are statically mapped, so when a packet generated by a customer-premises equipment (“CPE”) or switch port (edge switch) that has a label as stated above, the VLAN mapping switches that packet to the far end. The current standards modifications include a working to protection addressing change out at the end points, so that the end points change from the working path to the protecting path when that end point stops receiving packets from the far end port or CPE. Today, the method being used to generate a flip over is the loss of a specific number of subsequent 802.1AG packets from the far end. Packet network exhibit specific errors that can cause this method of fail-over to perform poorly.
PBT uses a 802.1AG “heartbeat” packet to determine whether a circuit is active and healthy. The heartbeat packet is called an Ethernet Operation Administration Measurement (“OAM”) packet. It's a session packet that goes from the source end to the destination end of the network and communicates that is has sent so many packets in between the last heartbeat packet and the current heartbeat packet. Using PBT, a network has a statically mapped working path and a protection path and the end points “listen” for the heartbeats and send packets with addressing to one of the two paths. When packets are no longer received, the end point changes it's addressing to take the alternate path. Currently, this detection is based on the lack of three sequential packets. There are two paths in a data network, and they are statically routed. Oftentimes, small amounts of packets are lost due to brief intermittent down periods in the circuit. This poor performance can be caused by circuit equipment losing synchronization (clock slips), congestion, maintenance activities (switch-overs), physical movement of the wires, electrical disturbances, and the like.
When the circuits go down, PBT switches from the working path to the protection path, and then back again, in response to each instance of three lost packets not being received at the far end. The current method causes packets to be continually readdressed until three consecutive packets are reached at the far end. Further, this flipping causes multiple hits down the line, which is stressful and damaging to the circuit equipment over time. This condition can have an echo effect when hierarchial heartbeats are used to tunnel one service through another path. This application links the failover of each tunnel to another and the delay time associated with failover can cause flipping.
In addition, today's PBT systems experience load sharing path failures, which may be caused by IEEE 802.3AD link protection with a bad path. The 802.3AD load shares two links by transmitting each packet over a different link If two switches are connected via Dense Wavelength Division Multiplexing (“DWDM”) and one path goes down, then every other packet crossing that path will be lost. This path won't switch given the number of specific number of packets lost does not equal three consecutive packets lost.